<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{padding: 0;margin: 0;}
        .box{
            width: 100px;
            height: 100px;
            background-color: #6ff;
            margin:10px;
        }
    </style>
</head>
<body>
    <?php
        echo "hello";

        for($i = 0; $i <= 10;$i++){
            echo "<div class='box'></div>";
        }
    
    ?>
    <div class="box"></div>
</body>
<script>
    var box = document.getElementsByClassName("box")[0];
    box.onclick = function(){
        alert(11111);
    }
</script>
</html>